The ever-growing demand of energy for modern society has prompted the need to develop efficient storage of electricity, meaning that one needs to have battery systems with high energy and power density, long lifetime and minimum production/disposal cost. In the last decade, a number of different battery systems such as nickel-metal hydride, sodium-sulfur, and lithium ion systems were found to have high potential for electric vehicles. Among them, lithium ion battery is considered to be the most promising candidate for this demanding application.
Conventional lithium ion batteries utilizing carbonate electrolytes provide working voltage of around 3.2-3.8 V and stable charging voltage up to around 4.3 V. The electrolyte becomes unstable at elevated voltages and may result in reduced cycle life and decreased safety of the lithium ion battery. There is, therefore, a need for improved electrolytes stable at an elevated voltage, such as greater than 5 V. There is also a need for further improving the reliability and performance of the batteries at high charging voltages.